Abnormal behavior in dogs can
have a variety of medical causes; it also can reflect underlying problems of a
psychological nature. Your veterinarian follows a systematic diagnostic approach in
searching for medical causes when a per exhibits unusual or unacceptable behavior.
As summarized by Landsberg (Canadian Veterinary Journal, 31:225-227, 1990), this includes:

6) more
specialized neurological examinations such as an electroencephalography and computerized
axial tomography scan.

Diagnostic steps 1 through
3 are usually completed first; additional tests such as steps 4 through 6 are performed if
indicated. If these test results prove to be negative, a veterinary behavior
consultant or qualified pet behavior therapist should evaluate the dog.

Inheritance has been shown
to play an important part in the behavior of both animals and humans; Plomin recently
reviewed its role (Science, 248:183-188, 1990). The genetic influence on behavioral
disorders rarely accounts for more than half of the phenotypic expression of behavioral
differences. Each of the multiple genes involved has a small effect on
behavior. Newer techniques in molecular biology should permit the identification of
the genetic DNA marker sequences responsible for behavioral variation.

However, behavior is the
most complex phenotype because it not only reflects the functioning of the whole organism,
but it is dynamic and changes in response to environmental influences. With respect
to animal behavior, applied behavioral genetics first was studied several thousand years
ago because animals were bred and selected for their behavior as much as their
conformation. The results can be attested to by the dramatic differences in behavior
and physique among various dog breeds. Today these breeds have a great range of
genetic and behavioral variability.

In recent years, many
investigators have noted the sudden onset of behavioral changes in dogs around the time of
puberty. Most of the dogs have been purebreds or crossbreds with an apparent
predilection for certain breeds (e.g., Golden Retrievers, Shetland Sheepdogs, German
Shepherds, Cocker Spaniels, Akitas, Doberman Pincschers and Rottweilers). Many of
these dogs also had begun to show the seasonal effects of allergies to inhalants and
ectoparasites such as fleas, followed by the onset of skin and coat disorders, including
pyoderma, allergic dermatitis, alopecia and intense itching.

A typical history starts
out with a quiet, well-mannered and sweet natured puppy. The dog is outgoing, has
attended puppy training classes to prepare for obedience, working or show events, and
comes from a reputable breeder whose kennel has no history of behavioral problems.

However, at the onset of
puberty, which varies from seven months to a year in age, sudden major changes in
personality are observed. Typical signs may include incessant whining, nervousness,
schizoid behavior, fear in the presence of strangers, hyperventilation, undue sweating,
occasional disorientation and failure to be attentive. These can progress to sudden
unprovoked aggressiveness in unfamiliar situations with other animals and with people,
especially children.

The owners may attribute
the problems to the sex hormonal changes accompanying puberty or just the uncertainties of
adolescent development. Often these animals are neutered, which appears to alleviate
the behavioral problems, specifically the aggression, for varying lengths of time.
For a significant proportion of these animals, however, neutering does not alter the
symptoms and they intensify progressively to the point that the adult can be described as
flaky, unable to handle any kind of stress, frantically circling, hyperventilating and not
able to settle down. Animals used for field work and tracking often fail to follow
the scent, whereas those in obedience training may lose the scent articles. Their
powers of concentration are often very short and so dogs that were training very
successfully at obedience appear to lag behind in a disinterested fashion. With all
of these changes in behavior, the problem of most concern is unwarranted aggression.
When large breeds are affected it poses a significant hazard to family members, friends
and strangers.

In some cases affected
animals do not show aggression but become very shy and fearful to the point that they are
social outcasts and do not make acceptable house pets. These animals clearly are not
suitable for show, obedience or working purposes. Some of these dogs will show
extremely submissive behavior, roll over and urinate upon being approached.

The third group of dogs
showing aberrant behavior consists of those that experience seizure or seizure-like
disorders beginning in puberty and continuing to mid-life. These are dogs that
appear perfectly healthy outwardly and have normal hair coats and energy, but suddenly
experience seizures for no apparent reason. The seizures are often spaced several
weeks to months apart, and occasionally they appear in a brief cluster. In some
cases the animals become aggressive and attack those around them shortly before or after
having one of these seizure episodes.

The number of dogs showing
various types of abnormal behavior in these three classical modes (aggression, extreme
shyness or seizure-like activity) has been increasing over the last decade.
Veterinary colleagues have remarked that in recent years some young dogs have become
completely unacceptable because of bizarre, sudden behavioral changes. Consequently,
we began to examine these animals by using the stepwise diagnostic approach outlined
previously. The importance of performing complete laboratory profiles in the blood
and urine, with specific emphasis on thyroid hormonal function was stressed.

We were surprised to find
that in many of the cases studied, significant abnormalities were found in the thyroid
profile. Some cases also had changes in the liver enzyme patterns, specifically with
abnormal increases in pre and post meal bile acids and elevated gamma glutamyl transerase
levels. About 10 percent of these young dogs had abnormalities of the liver profile
and a few also had changes in renal function. For the majority, however, the primary
abnormality was attributable to abnormal thyroid function. This thyroid dysfunction
would classically express high levels of T3 and T4 autoantibodies with an artifactual,
apparent elevation of total T3 level. It would not be uncommon to find circulating
total T3 levels that read as much as 3,000 to 5,000 nanograms per deciliter. While
not all of the affected animals had documented evidence of T3 and T4 autoantibodies, some
of these had positive antithyroglobulin antibody tests. In either event, the
diagnosis was confirmed as autoimmune thyroiditis.

The autoimmune thyroid
disease present in these patients apparently is inducing some type of physiological change
at the cellular lever, which leads to the aberrant behavior. This supposition can be
made with some assurance because treatment of thyroiditis of these dogs with appropriate
doses of thyroid replacement hormone given twice daily along with a one-month tapering
course of low-dose corticosteroids, has successfully reversed the behavioral problems
within four to eight weeks. Dramatic changes in behavior have been recognized in a
few cases as early as after 10 days of therapy.

By contrast, it usually
takes five to seven months of thyroid replacement therapy to effect complete disappearance
of the circulating antithyroid antibodies. These dogs should be maintained for life
on the appropriate dose of thyroid hormone, which may need to be adjusted periodically.

Another subset of affected
dogs consists of those that do not have demonstrable antithyroid antibodies but have
baseline thyroid profiles that are clearly abnormal. In these cases, levels of total
T4, total T3, free T4 and free T3 are usually well below the lowest limits of the adult
normal ranges or are in the low normal or borderline ranges. The latter situation is
of particular significance in young dogs of nine to 15 months of age. When these
dogs are treated with standard doses of thyroid replacement therapy (0.1 milliliter per 10
pound of body weight, given twice daily) the clinical signs associated with abnormal
behavior rapidly resolve.

To date (October 1992)
more than 25 animals have been diagnosed as having thyroid imbalance as the major, if not
exclusive, cause of their behavioral abnormalities. Some of these animals have been
followed for as long as three years and are still exhibiting anormal behavior.
Animals on therapy have returned successfully to obedience activities, completed show
championships and undertaken active field and tracking work.

Here are two case studies
as examples:

In the first, a
four-year-old male Akita, weighing 110 pounds, suddenly attacked his owner and bit her in
the face. The dog had been owned by the same family since early puppyhood and had
been a remarkably even tempered, well-behaved and non-aggressive pet with people and other
animals. After seeking the advice of two different veterinary clinicians and a major
teaching hospital, the owner was about to give up in despair because no physical
abnormalities could be found.

She was referred to us by
an Akita rescue group, as this pattern of behavioral change has been associated with
thyroid dysfunction in the breed. A complete thyroid panel which had not been
performed earlier, was suggested and the dog was found to be hypothyroid. Thyroid
therapy was initiated on a twice-daily basis. The dog's exemplary temperament
returned and he has not shown any unusual behavior for more than a year. An
interesting additional complication of the case was a moderately severe thrombocytopenia
which also resolved with low doses of alternate-day steroid therapy and thyroid
medication.

In the second, a
nine month old male Shetland Sheepdog from excellent show-quality bloodlines
suddenly became frantic and fearful. Acting intermittently, as if his
vision were impaired, he attacked a toddler in the owner's home. A
complete physical examination was given and laboratory testing done; a routine
check for T4 was borderline normal. The dog's abnormal behavior appeared
to resolve, but soon reappeared.

After a second attack the
dog had a complete thyroid profile done at Michigan State University's Animal Health
Diagnostic Laboratory. The total T4 was 44 nmol/1; total T3 was 0 nmol/1; free
T4 was 2 pmol/1; free T3 was >20 pmol/1; T4 autoantibody was 18 and T3 autoantibody was
85. The referring veterinarian did not realize that the results were consistent with
autoimmune thyroiditis and the dog was not treated. Two months later the dog
attacked another person and a second thyroid profile was sent to the Michigan State
Laboratory. The second profile showed a total T4 of 29 nmol/1; total T3 of 0 nmol/1;
free T4 of 25 pmol/1; free T3 of >20 pmol/1; T4 autoantibody of 48 and T3 autoantibody
of 91. Consultation with our group was made at this point.

The dog had a previous
history of facial demodectic mange; because corticosteroids are not recommended with
demodecosis, the treatment consisted for a full therapeutic dose of T4 thyroid supplement
at 0.1 milligram per 10 pounds and a one-third dose of T3 thyroid supplement at 1
microgram per pound, both given twice daily. The rationale for treating with both T4
and T3 supplements in this case was to attempt to normalize the thyroid axis as quickly as
possible to avoid danger to family members. At the time of this writing the dog's
behavioral aggression has subsided.

For those animals that
show occasional seizure disorders, thyroid medication alone usually will suffice.
Anticonvulsant medication is needed along with the thyroid therapy to control cases with
more severe seizure clusters. The anticonvulsants of choice would be phenobarbital
or, alternatively, sodium bromide, particularly if the patient has abnormalities of liver
function.

Because many of these
animals have autoimmune thyroid disease, concomitant medical management includes avoiding
environmental factors that can further challenge the immune system. This means
placing the animal on a hypoallergenic "natural" diet preserved with vitamins E
and C (e.g., lamb and rice based lower-protein kibble without added chemical
preservatives); avoiding drugs such as the potentiated sulfonamide antibiotics and monthly
heartworm preventatives that may adversely affect the immune system in these susceptible
dogs; and withholding vaccination boosters until the thyroid function is balanced properly
and the behavioral abnormalities are resolved. If animals are due for annual vaccine
boosters during this period, vaccine antibody titers for distemper and parvovirus can be
determined.

If your otherwise healthy
young or adult dog experiences sudden behavioral changes, you should consult your vet and
check for an underlying thyroid imbalance as shown by:

1) The presence of
thyroid autoantibodies

2) Low or
borderline levels of total T4, total T2 and Free T4 or

3) Failure to
triple baseline total T4 levels in response to challenge with thyroid-stimulating hormone.

In our experience, the
most predictive thyroid test parameters to identify these cases are 1 and 2, because the
thyroid stimulating hormone response test just measures thyroid reserve, which remains
adequate in the early stages of thyroid disease.